Telomer acid process



United States Patent TELOMERACID PROCESS William S. Barnhart, Cranford,andRobert H. Wade, West Paterson, NJ., assignors, by mesne assignments,to Minnesota Mining and Manufacturing Company, St. Paul, Minn, acorporation of Delaware No Drawing. Application August 28, 1956 SerialNo. 606,568

7 Claims. (Cl. 260-408) This invention relates to an improved processfor the preparation of telomer acids.

In copending application Serial No. 452,705, filed August 27, 1954,there is disclosed a new class of telomer acids which are preparedby thehydrolysis of perhalo genated telomers, the tel-omers being prepared bythe telomerization of perhalogenated monomers such aschlorotrifluoroethylene, tetrafluoroethylene, and unsymmetricaldichlorodifiuoroethylene with telogens such as sulfuryl chloride,sulfuryl bromide, fluorosulfuryl chloride and brornosulfuryl chloride.The hydrolysis of cotelomers of the foregoing monomers with suchcornonomers as symmetrical clichlorodifiuoroethylene and vinylidenefluoride is also disclosed. I

The preferred telomer acids are monoacids having the formula.

Cl( CFz-CFCD CF COOH and diacids having the formulain which n is aninteger from 2 to .16, these acids being produced by the hydrolysis ofthe telomerization product of chlorotrifluoroethylene with sulfurylchloride, the telomer having the formula in which n is as given above.

The telomer acids have many uses such as emulsifiers inaqueouspolymerizatio-n systems as disclosed in copending applicationSerial No. 463,073, filed October 18, 1954, and also have many otheruses as surfactants, as disclosed in copending application Serial No.526,537, filed August 4, 1955.

Generally speaking, the telomer monoacids -are more desirable than arethe diacids due'to thegreater number of uses existing for the monoacids,and, in accordance with the present invention, a process isprovidedwherein the ratio or" monoacid to diacid formed in the'hydrolysisproduct is higher than that previously attainable. Both 7 mono anddiacids are formed in the hydrolysis product but it is desirable tomaintain the quantity of diacid formed as low as possible. The desirableresults of the invention, i.e., the increase of mono-to diacid ratio inthe product, are obtained by the addition of a telomer monoor diacid tothe reaction mixture as'an emulsifier before reaction is initiated. Theparticular monoor diacid used can be any of the C t C32 telomer acids.

In the process of the invention, a iperhalogenated telomer, such as'thetelomer obtained from the telomerization of polychlorotrifluoroethylenewith sulfuryl chloride, oleum, and a telomer monoor .diacid are chargedto a reactor and maintained atanelevated temperature and Patented Sept.15, 1959 ICC 2 pressure until the reaction is complete. The quantity ofoleum charged to the reactor may be in the range of about 2 to 10 molesper mole of telomer and the oleum may have a concentration in the rangeof about 1 to 70 percent free sulfur trioxide, although it is preferredto use oleum having a concentration in the range of about 1 to 20percent free sulfur trioxide. The telomer acid emulsifier is added in aconcentration of about 1 to 10 percent by weight, preferably about 2 to5 percent by weight based upon the reaction mixture.

The temperature of reaction is in the range of to 250 C., preferably 180to 240 C. The use of the telomer acid emulsifier permits a lowerreaction temperature than heretofore since the optimum reactiontemperature previously was about 220 C. whereas with the use of anemulsifier a satisfactory reaction rate is obtained at 200 C. Thereaction time may be between about 15 and 40 hours, but the highestyield of desired products are obtained when operating at a temperatureof 200 C. for a period of 24 hours. The reaction pressure 'may be in therange of about atmospheric to 150 p.s.i.g. and is preferably in therange of about 30 p.s.i.g. to 125 p.s.i.g. The pressure can also bevaried for other purposes, for example, to cause certain products suchas chlorosulfonic acid to remain in the reaction mixture or to permit itto distill.

At the completion of the reaction period, the reaction mixture is cooledto a temperature of about 120 C. or lower by indirect heat exchange andis transferred to a drowning tank where it is cooled and diluted withwater to effect the separation of a product layer and an aqueoussulfuric acid layer. The cooling and dilution of the reactionmixture isconveniently eifected by the addition of ice thereto, with or withoutadditional water.

Cooling and dilution of the reaction mixture constitutes a simple andeffective means for the separation of the desired telomer acid productlayer from the sulfuric acid layer since the solubility of telomer acidsin dilute sulfuric acid, having a concentration in the range of about'30 to 70 percent by weight, is very low. I v i The sulfuric acid layermay be extracted with a solvent such as benzene, carbon tetrachloride,or other halogenat'ed methylenes or ethylenes, in order to recoverwhatever small quantities of dissolved telomer acids may remain in thesulfuric :acid layer, and the extract may then be added to the productlayer. 0

The product and extract layers are then transferred to a wash tank Wherethey are washed with dilute sulfuric acid and, from the wash tank, themixed telomer 'a'cids are transferred to an acid still where they aredistilled to recover the various products of the process. From the acidstill, telomer diacids are recovered as bottoms fractions while telomermonoacid is recovered as an overhead fraction, the final distillationbeing performed at a reduced pressure in the range of l to 100 Hg.absolute.

The improved process of the invention is most practical when the monoordiacid emulsifier has the same carbon content as the telomer beinghydrolyzed as this contingency allows the emulsifier and product to becollected together since they are identical. If the emulsifier has adifferent carbon content than the telomer, then the problem ofseparating the two remains. f

The high yield of monoacid relative to the, yield of diacid obtainedusing an emulsifier may be the result of several factors. The emulsifierprovides better contact between the telomer and oleum thereby increasingthe rate of reaction. This rate factor in conjunction a lower reactiontemperature apparently favors the production of monoacid. The mechanismof diacid formation may proceed from the monoacid throughan'isomerization step followed by or simultaneous with hydrolysis asindicated by the following:

F2010 F 010 F20 F 010F20 OX 0 F 0120 F20 F20 F 010 F20 OX lH2SO4 X0 0 0F 0 FzCFClC F20 0X lHgO H020 C F20 F20 F 010 F20 02H wherein X=Cl or F.

The advantages of adding a telomer acid as an emul sifier to a processwhich produces telomer acid may be explained by the following equation:

since if this equation correctly describes the reaction course, thefinal telomer acid product is obtained only at the end of the reactionwhen the mixture is diluted with water as this step converts the telomeracid halide to the telomer acid. From this, it can be assumed that .thetelomer acid is superior to the telomer acid halide as an emulsifier.

The invention will be further illustrated by reference to the followingspecific examples:

EXAMPLE 1 A series of weight balance variable studies was con ducted toevaluate the use of catalysts, emulsifiers and favorabletime-temperature relationships for maximum monoacid production. Theequipment consisted of a 1 liter, single-necked flask fitted forstirring and the distillation of low boiling by-products as formed. Ineach experiment 1.3 moles of tetramer. having the formula Cl(CF CFCl)Cl, and a 5 to 1 mole ratio of 5 percent oleum, were used in eachexperiment. Three runs are summarized below, and Experiment 1 gave noimprovement in the conversion ratio using a reaction temperature of 180C. and a reaction time of 48 hours. In the second experiment, the use ofcopper sulfate catalyst, a reaction temperature of 200 C. and a reactiontime of 24 hours actually gave less conversion to acids than a similarrun without the addition of the salt; the conversion ratio improvementwas negligible. The third experiment was run with the addition of 70grams of diacid to facilitate telomer-sulfuric acid contact; a goodconversion to monoacid and a much improved conversion ratio wasobtained.

Table 1 Expt. 1 2 3 48 24 24 180 200 200 Additive none 01(CFn-CFCD401(Recovery):

grams 274 301 149 males 0. 508 0. 559 0. 278 moles used 0. 809 O. 751 1.029 CKCFz-CFCUsCFzCOOH' grams 296 259 393 moles 0. 619 0. 540 0. 821percent c0nversion 47. 0 41. 2 62. 8 percent yield 76. 5 71. 9 79. 8 HOO OOF2(OFg-CFO1)2OFZOOOHI grams 73. 8 52. 5 45. 2 moles 0. 168 0. 120 0.103 percent conversion 12. 8 9. 2 7. 9 percent yield 20. 8 16. 0 l0. 0otal:

mnlpe 1. 295 1. 219 1. 202 percent conversion 59. 8 50. 4 70.7 percentyield 97. 3 87. 9 89. 8 percent recovery 98. 4 93. 9 92.0 Ratio:Conversion to monoacid/Conversion to diacid 3. 68 4. 48 7. 95

Table 2 TELOMER ACID STUDIES Run No 1 2 Tplnmer Tetramer Tetramer Kg67.0 56. 8 124. 8 106 101% H230 kg 65. 0 57. 7 Emnleifier 110116 1Z2 l.6 Pressure, p.s.i.g 60 Time, hrs. 24 24 Temp, G 220 200 Product:

Telomer, kg 8. 6 10.7 moles 16. 0 20. 0 Monoacid, kg 25. 9 32.6 (-1.6)moles. 54. 2 64. 6 Diacid, kg 14. 4 5. 8 moles 32. 8 13. 2

Conversion, percent:

Monoacid 43. 7 61. 0 Diacid 26. 3 12, 5

Total 70. 0 73. 5

Yield, percent:

Monoacid 50. 1 75. 0 Diacld 30. 2 15, 3

Total 80. 3 90. 3

Recovery mole percent 82. 6 92.3 Ratio, mono-[diacid 1. 66 4. ss

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all suchmodifications. This application is a continuation-in-part of our priorand co pending application S.N. 452,703, now U.S. 2,806,865 and S.N.452,705, now U.S. 2,806,866.

We claim:

1. An improved process for the preparation of a perhalogenatedcarboxylic acid which comprises treating with fuming sulfuric acid at atemperature between about 175 C. and about 250 C. a fluorine containingtelomer of the formula Cl(CF CFCl),,Cl where n is an integer from 2 to16 in the presence of an added amount of said perhalogenated carboxylicacid, cooling the reaction mixture and subsequently treating thereaction product with water and recovering the acid produced.

2. The process of claim 1 wherein the perhalogenated carboxylic acid isa monocarboxylic acid.

3. The process of claim 1 wherein the perhalogenated carboxylic acid isa dicarboxylic acid.

4. An improved process for the preparation of a perhalogenatedcarboxylic acid which comprises treating with fuming sulfuric acid at atemperature between about 175 C. and about 250 C. and at a pressure inthe range of about 5 to p.s.i.g. Cl(CF CFCl),,Cl where n is an integerfrom 2 to 16 in the presence of a prehalogenated acid of the formula inwhich n is as above, cooling the reaction mixture and subsequentlytreating the reaction product with water and recovering the acidproduced.

5. The process of claim 4 wherein n is 3.

6. The process of claim 4 wherein n is 4.

7. A process which comprises charging to a reactor (a) perhalogenatedtelomer having the formula 5 6 where n is an integer from 2 to 16, (b)oleum and (0) References Cited in the file of this patent an emulsifierselected from the group consisting of perhalogenated monoacids havingthe formula UNITED STATES PATENTS 2,766,215 Stoops et a1 Oct. 9, 1956 C1CF 2 CFCD"-1CF2COOI I 5 2,806,865 Barnhart et a1. Sept. 17, 1957 inWhlch n 18 as given above, and diaclds havmg the 2,30 B h t t 1, Sept.17, 1957 formula HOOCCF (CF -CFC1),, CF C00H in which n is as givenabove; thereafter reacting the aforemen- OTHER REFERENCES tionedmaterials at a temperature between about 175 C. to about 250 0.; coolingthe reaction mixture; and MacArdle: The Use of Solvents 1n OrgamcChemutry,

10 subsequently treating the reaction product with water and PP- 1 and 2Van Nostrand New Yorkrecovering said reaction product.

1. AN IMPROVED PROCESS FOR THE PREPARATION OF A PERHALOGENATEDCARBOXYLIC ACID WHICH COMPRISES TREATING WITH FUMING SULFURIC ACID AT ATEMPERATURE BETWEEN ABOUT 175* C. AND ABOUT 250* C. A FLUORINECONTAINING TELOMER OF THE FROMULA C1(CF2CFC1)NC1 WHERE N IS AN INTEGERFROM 2 TO 16 IN THE PRESENCE OF AN ADDED AMOUNT OF SAID PERHALOGENATEDCARBOXYLIC ACID, COOLING THE REACTION MIXTURE AND SUBSEQUENTLY TREATINGTHE REACTION PRODUCT WITH WATER AND RECOVERING THE ACID PRODUCED.